Sparking plug for internal combustion engines



2 Sheets-Sheet 1 INVENTOH zgd/f @ya 6221417 March 13, 1934. D, coRBlN SPARKING PLUG FOR INTERNAL COMBUSTION ENGINES Filed Feb. 23, 1932- n. A 1 1 r 1 l. 1111 1 1fr11 11 #7 .1.11/1/1.71 y 1 1 1 1 1.1.1.1./ 11 1.1 mm/11 11 /1 1111 11 111.1 1.1 1 #1.111 1 7mm/F1 111111111 1 111/ 1111 11/ 111./ 1.1 1.1 1 1 1.1 1 11111111111 1 11 1 11/111 /1 .J1 .1 1 11111 1 111 1 1 .1 1 11 1 11 111 11111.. 1 1 1 1111 1 1 11. v1.1 f 17A 24|- 11 1 1111 1 11. v1 11 1 1 .1u 1

March 13, 1934. D. H. coRBlN 1,950,596

l I SPARKING `PLUG' FOR INTERNAL COMBUSTIO'N ENGINES Filed Feb.

afina/y! .Z a ///f////////////// /W/M//// d e e f, gn/M @wo W N W Patented Mar. 13, 1934 y 1,950,596

UNITED STATES PATENT OFFICE i SPARKING PLUG FOR INTERNAL CQIWBUSTION ENGINES Douglas Haynes Corbin, Birmingham, England Application February 23, 1932, Serial No. 594,487

LIn Great Britain April 13, 1931 Claims. (Cl. 12S-169) This invention relates to the central elecbecomes enclosed within and therefore supported trode and insulating sleeve therefor of sparkby the metal housing of the sparking plug. ing plugs for internal combustion engines. The screw thread in the bore of the sleeve is The object of the invention is to secure the of comparatively steep pitch to match the nec- E central electrode in the insulating sleeve of a essarily somewhat coarse interrupted screw 6G sparking plug in a manner which avoids undue thread constituted by the projections. strains being' imposed on the insulating sleeve Preferably theindented-embossed interrupted as a result of differential temperature-induced screw thread projections on the rod are closely expansion of these parts. The invention also adjacent and extend along only a small portion 10 avoids imposing undue stresses on a weak portion of the length of the rod, thus leaving the major 65 of the insulating sleeve, and undue recessing and portion of the rod smooth.

kweakening of this latter. Moreover the inven- The indented-embossed projections on the rod tion facilitates manufacture of the respective `may be 10Cated approximately at the mid-length portions of the sparking plus. of the insulating sleeve. In such ease, the cumull With the form of sparking plug which the inlativeiy increasing relative displacement, due te 70 VlntOn iS designed C0 impOVe, htheltO the C911- expansion, is considerably reduced, as it proceeds al Wire Tod electrode has been Secured t0 a outwards from the middle anchorage towards coaxial terminal screw extension of larger diamboth ends of the sleeve7 instead of from one end eter, Which SCTGWS HO a SCleW-thleaded enlarge* thereof along the entire length of the sleeve.

to ment of the respective end portion of the axial The bore of the sleeve ls cemented Accord- 76 bore 0f the usual porcelain insulating 5193i@ ing to a further feature of the invention, which The screw threaded interconnection of these two ls Capable of employmenlJ also in existing types parts is therefore located at the respective someof sparking plugs, for instance those inwhich What unsupported .Outer end of the msulating the central electrode is anchored in the outer end a@ Sleeve' Whlch end 1S already weakened by the of the insulating sleeve by a terminal screw as 89 enlargement of the bore thereof. The terminal above describedy the Smooth pol-tions of the screw cannot be extended a considerable dis- I length of the central rod electrode are shielded tance into the sleeve wlthout weakening the by a coating of lacquer or other Suitable adhe sleeve by the consequent extension of the en- A s1on-prevent1ng substance, such as parainn wax, 3o largement of the bore thereof and without inparafne oil or the hke, from rm adhesion in the troducing diiiculty 1n keeping the screw thread cemented bore of the 51e eve.

of the sleeve reasonably accurate to iit a long By shielding with lacquer or other su1table length of screw, and other difculties of manuadhesiompreventing Substance the s 00th pop facture. Moreover, by the anchoring of the central electrode at the cuter end of the insulating mons of the. mg whnst lem/mg theportlqn beard sleeve, diierential expansion, under increase of mg theprogectloris exposed only thls pomo an temperature, of the sleeve and central electrode, the projectlons Wm become rmly adherent to the involves a displacement of the central electrode cmenteq bore @f the Sleev' Consquerftly on relatively to the Sleave which cumulatlvely im differentialexpansion occurr1ng,relat1ve d1splace- 40 creases along the length of the electrode. The ment 0f the Sleeve and rod can take P1355@ with' 95 I present invention enables this cumulatively 'inout straining the S1eeVecreasing relative displacement to be considerably Representatw @XalnpleS 0f the lnventlon are reduced illustrated on the accompanying drawings, 1n

Now according to the Vmain feature of the Which:-

present invention, whilst the bore of the insu- Fig# 1 S a longitudinal SGC'OI! thrOllgh the 10g lating sleeve of a sparking plug isof a diameter insulating sleeve, central wire electrode and terto fit the central wire rod electrode, such small mina-1 SCIGW 0f a sparking plug.

bore is formed' with a screw thread extending Fig. 2 isa transverse section alone the line 2-2 along a considerable length of the bore, and the 0f Fig. l, and l central wire rod electrode is indented, for in- Fig.' 3 is across section ofthe oentrajliwire rod 105 stance at two or more situations, so as to emsi electrode at one of the indented-embossed proboss lateral projections helically situated'as porjections thereof.

tions of an interrupted screw thread on the rod Fig. 4 vis a broken longitudinal sectional elevaand engaging with the screw thread in the bore, tion showing a modified form of attachment oi.'

at a portion of thelength of the sleeve whichy the terminal screw. 110 Y Fig. 5 is a longitudinal section of a central wire electrode with an integral terminal screw.

Referring more particularly to Fig. l, a1 is the metal housing oi a sparking plug, in which is the insulating sleeve a of the sparking plug. b is the central wire rod electrode of the sparking plug.

The insulating sleeve a is formed throughout its length with a bore c of a .diameter to t the wire rod electrode b, and the bore c is steeply screw threaded from the outer end of the sleeve a to beyond the mid-length thereof.

At about its mid-length the wire rod electrode b is indented at intervals to form projections e thereon. These projections e are located to constitute portions ot an interrupted screw thread on the wire rod b, whereby the latter can be screwed into and held in the bore c of the insulating sleeve a, by engagement .with the screw thread of the bore.

The rod b is thus held in the insulating sleeve a at a portion thereof within and protected by the usual metal housing a1 of the sparking plug. Moreover, on differential expansion taking place, the smooth portions of the rod b on each side of the portion bearing the projections e can displace themselves outwards away from the anchorage by the projections e, whereby the relative displacement between the sleeve a and rod b is rendered small.

The rod b is permanently secured in the bore c by cement. However, the outer smooth portions o! the rod b may be coated with lacquer or other suitable adhesion-preventing substance so that the cement does not attach them to the bore c oi' the insulating sleeve a. These smooth portions of the rod b are therefore free to become displaced by expansion without any restraint other than that imposed by friction against the cemented bore c.

The lacquered lengths of the rod b extend for example along d, d. f is the terminal screw of the central wire rod electrode b. In the construction illustrated in Fig. l, the terminal screw f formed with a collar a, has a short tubular socket h, into the bore of which the end of the rod b is inserted. The tubular socket h is indented at i, which forces the metal of the socket h into corresponding indentations j in the portion of the rod b inserted in the sleeve h. The rod b and screw f are thus permanently rigidly united.

k is a nbre washer interposed between the collar g and the respective end of the insulating sleeve a.

In the alternative arrangement illustrated in Fig. 4, the end of the rod b is knurled at b1 to facilitate its being screwedinto the bore c of the' insulating sleeve a, and to promote metallic contact and therefore electrical continuity with the terminal screw f. Also the collar g of the terminal screw f is of a diameter to extend wider than the end of the insulating sleeve a and at its periphery is rolled and clinched over a bead l on the insulating sleeve a. The knurled end b1 of the rod b merely nts in the bore of the socket h of the terminal screw f.

In the construction shown in Fig. 5, the terminal screw ,f and collar g are formed integrally on the wire rod b, by a cold heading operation, or alternatively in a machine which gathers the wire at the same time as it heats it electrically.

As usual, the insulating sleeve u. is of porcelain. The screw thread in the bore c of the insulating sleeve a can be formed by a tap advanced into the clay blank whilst the external surface thereof is subjected to the usual turning operation.

I claim:

l. In a sparking plug, a metal housing, an insulating-sleeve in said housing and having a coarsely screw threaded bore of substantially uniform diameter, a smooth central wire rod electrode extending along said bore, and closely mutually adjacent embossed lateral projections on and extending along only a small portion of the mid-length portion of said rod and helically situated as portions of an interrupted screw thread engaged with said screw threaded bore at a portion of the length of said insulating sleeve enclosed by said metal housing.

2. In a sparking plug, a metal housing, an insulating sleeve in said housing and having a coarsely screw threaded bore of substantially uniform diameter, a smooth central wire rod electrode extending along said lbore, and closely adjacent embossed lateral projectms upon and located between the ends of said rod and which projections engage with the thread in said screw threaded bore approximately at the mid-length of said insulating sleeve.

3. In a sparking plug, a metal housing. an insulating sleeve in said housing and having a. bore, a central wire rod electrode tting and secured in said bore, a terminal screw, and a socket of said terminal screw iltted over an indented end of said central rod, said terminal screw being secured to said rod by indenting said socket into said indentations of said rod.

4. In a sparking plug, a metal housing, an insulating sleeve in said housing and hcvng a bore, a bead on said insulating sleeve, a central Wire rod electrode fitting and secured in said bore, a terminal screw, a socket of said terminal screw iltted over an end of said rod, and a collar on said terminal screw clinched over said bead on said insulating sleeve.

5. In a sparking plug, a metal housing, an

insulating sleeve in said housing and having a coarsely screw threaded bore of substantially bore.

i DOUGLAS HAYNES CORBIN. 

